C++ で簡単な投票システムを作成するにはどうすればよいですか?

#include <iostream>
#include <vector>

using namespace std;

// Voter class
class Voter {
    string name;
    int age;
    string gender;
    bool voted;

public:
    Voter(string n, int a, string g) {
        name = n;
        age = a;
        gender = g;
        voted = false;
    }

    bool hasVoted() {
        return voted;
    }

    void setVoted() {
        voted = true;
    }
};

// Vote class
class Vote {
    string name;
    int id;
    vector<string> candidates;
    vector<int> votes;

public:
    Vote(string n, int i) {
        name = n;
        id = i;
    }

    void addCandidate(string candidate) {
        candidates.push_back(candidate);
        votes.push_back(0);
    }

    void castVote(int candidateIndex) {
        votes[candidateIndex]++;
    }

    void printResults() {
        for (int i = 0; i < candidates.size(); i++) {
            cout << candidates[i] << ": " << votes[i] << " votes" << endl;
        }
    }
};

// VotingSystem class
class VotingSystem {
    vector<Voter> voters;
    vector<Vote> votes;

public:
    void registerVoter(string name, int age, string gender) {
        Voter voter(name, age, gender);
        voters.push_back(voter);
    }

    void createVote(string name, int id) {
        Vote vote(name, id);
        votes.push_back(vote);
    }

    void addCandidate(int voteIndex, string candidate) {
        votes[voteIndex].addCandidate(candidate);
    }

    void castVote(int voteIndex, int candidateIndex, int voterIndex) {
        if (!voters[voterIndex].hasVoted()) {
            votes[voteIndex].castVote(candidateIndex);
            voters[voterIndex].setVoted();
        }
    }

    void printVoteResults(int voteIndex) {
        votes[voteIndex].printResults();
    }
};

int main() {
    VotingSystem votingSystem;

    // Register voters
    votingSystem.registerVoter("Alice", 25, "female");
    votingSystem.registerVoter("Bob", 30, "male");
    votingSystem.registerVoter("Charlie", 35, "male");

    // Create vote
    votingSystem.createVote("Favorite color", 1);

    // Add candidates
    votingSystem.addCandidate(0, "Red");
    votingSystem.addCandidate(0, "Blue");
    votingSystem.addCandidate(0, "Green");

    // Cast votes
    votingSystem.castVote(0, 0, 0);
    votingSystem.castVote(0, 1, 1);
    votingSystem.castVote(0, 0, 2);

    // Print vote results
    votingSystem.printVoteResults(0);

    return 0;
}